NASA Estimates 21 Rogue Planets per Star in Milky Way, Implying Trillions of Worlds
Updated
Updated · spacedaily.com · Aug 13
NASA Estimates 21 Rogue Planets per Star in Milky Way, Implying Trillions of Worlds
1 articles · Updated · spacedaily.com · Aug 13
Summary
Six ultrashort microlensing events in a 3,535-event MOA survey underpin NASA’s estimate that the Milky Way may host about 21 free-floating or very wide-orbit planets for every star.
That headline figure is a model-based extrapolation, not a direct count: the study’s one-sigma range runs from roughly eight to 44 planets per star, leaving the true total substantially uncertain.
Microlensing detects these dim objects through brief brightening of background stars; the shortest candidate signal lasted 0.057 days, or about 82 minutes, and pointed to a lens near Earth mass.
The study also narrows the claim behind “rogue planets,” because some objects may still orbit stars at distances too wide to leave a clear host signature.
NASA says the Roman Space Telescope, now targeted for launch on Aug. 30, 2026, should test the steep low-mass distribution behind the estimate and turn today’s extrapolation into a stronger census.